This invention relates to a heating appliance and more particularly to a microwave heating appliance with capability of deciding based upon timewise variations in a voltage at a terminal of such an atmosphere sensor as a gas sensor, what kind of foodstuff is being heated and if the heating of the foodstuff is completed.
In the recent years, automatic cooking appliances of the microwave oven type have been placed on the market, in which an atmosphere sensor such as a gas sensor is installed to aid the appliance in deciding if the cooking of the foodstuff is completed. This sort of appliances however further requires a predetermined number of keys which are assigned to different kinds of foodstuffs to set unique heating temperatures, with the result in user inconvenience in using the appliances.
As seen in FIG. 1 illustrating a conventional appliance, the predetermined number of keys K.sub.1, K.sub.2, K.sub.3 and so forth are provided for different kinds of foodstuffs. Different heating temperatures are preset in conjunction with each of these keys. Typically, the heating temperature is 70.degree.-80.degree. C. for the first key K.sub.1 appropriate for side dishes and china bowl, 50.degree.-60.degree. C. for the second key K.sub.2 appropriate for heated "sake" and about 100.degree. C. for prepared or preheated material such as spinach. The user must select one of these keys and sets a desired heating temperature, depending upon what kind of foodstuff is to be heated.